Industrial make-up air lowest temperature?
Industrial make-up air lowest temperature?
(OP)
I'm doing a high level review for an industrial HVAC system where the indoor temperature is too high in both summer and winter. There is a lot of heat and moisture produced by the process in the plant and the ventilation is not enough. I understand that air change is not a good criteria for judging and designing an industrial HVAC system, but currently the plant has about 3 ACH of ventilation in the winter. It is mostly limited by the make-up air unit because in the summer they can turn on several extra exhaust fans and open the roll-up doors for ventilation.
I need to recommend several high-level recommendations for the retrofitting of their system. One option of course is the addition of MUA units. However, there should also be options where MUA units isn't added (for cost or real estate reasons).
What is the lowest temperature where untreated air can be introduced into the building before problem can occur? This is only for the additional ventilation on top of the existing MUA units. The building is large enough where the cold air won't freeze anything before it's mixed with the warm air inside. The outdoor air can get down to -40F.
I need to recommend several high-level recommendations for the retrofitting of their system. One option of course is the addition of MUA units. However, there should also be options where MUA units isn't added (for cost or real estate reasons).
What is the lowest temperature where untreated air can be introduced into the building before problem can occur? This is only for the additional ventilation on top of the existing MUA units. The building is large enough where the cold air won't freeze anything before it's mixed with the warm air inside. The outdoor air can get down to -40F.





RE: Industrial make-up air lowest temperature?
(The outdoor air can get down to -40F.)
you want to intreduce untreated outside air to a building, the temperature would be tha same outside, I couldn't find a reason to ask about lowest tepertature for non heated air.
correct me if I am wrong please
RE: Industrial make-up air lowest temperature?
The question is whether there is a recommended minimum temperature before the outside air cannot be introduced into the room untreated.
Let's say the minimum temperature is X degree.
If the outside air can get down to -40F, then there are two possibilities:
1. Bring in the outside air when the O/A temperature is above X degree, and stop the fans and close the damper when the temperature drops below X degree.
2. Bring in the outside air all winter long because X degree is below -40F.
In either case, we need to know what X degree is, if it exist at all.
RE: Industrial make-up air lowest temperature?
you have posted a question and someone asked you about a point, you do not have to be Impolite, high level of review needs high level of polite person
RE: Industrial make-up air lowest temperature?
If you are concerned about human comfort, there may be guidance in ASHRAE 55 or (heaven forbid) ASHRAE 62.1.
If the air is blowing on water pipes or people, you're going to have to temper the air or shut the dampers at a pretty warm temperature.
If you are concerned about freezing stuff only, temper your air to 35°F at a minimum. Heating loops with glycol are common. I don't know of a lower limit for makeup air, but a lower limit of discharge air is a comfort or freeze-up issue.
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies
RE: Industrial make-up air lowest temperature?
RE: Industrial make-up air lowest temperature?
as tys said, your main concern is how to mix introduced air to reach acceptable indoor supply scheme.
the only specific help you can get is the one from air distribution manufacturers. you need to find adequate diffusers, supply grilles or what you want, and you need to calculate air mixing by their recommendations, and, on the other hand, minimum air temperature is directly dependent on adopted air speed in occupied area.
ashrae handbook do have it somewhere - charts with air speed - air temperature relations, for different comfort criteria, including industrial. i don't know where it is, but i'm sure it exists as, for that specific issue i use european norms.
again, the lowest limit to start with is the one allowed in air distribution devices calculations, and you need to obey it as there is no other way to find out how to rectify cold draft issues. cold drafts can cause serious health troubles even at temperatures higher than interior design temperature, so that matter should have number one priority.
RE: Industrial make-up air lowest temperature?
Stick the following phrase in Google:
handbook of industrial ventilation
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies
RE: Industrial make-up air lowest temperature?
I have already read through the ASHRAE handbooks, journals, and several industrial ventilation handbooks. However, so far I haven't found a guideline or a method of determining the lower limit of MUA temperature. I was just hoping to get some extra ideas from experienced people. Thanks to those who provided ideas.
RE: Industrial make-up air lowest temperature?
In Summer when the OA temp is higher than the setpoint, you can do little to reduce the high temperature without greatly increasing your air change rate or adding some kind of cooling. As the OA is warmer and also more moist, you need to increase the air change rate to ensure the moisture coming from within is adequately purged. Your temp is going to be limited to OA + a delta of 5 or 10 degrees.
In unconditioned machine spaces, the OA demand for cooling usually far exceeds that required for adequate ventilation for the occupants, but please check your particular situation.